11 parts of the model so that a wide range of geometric can be achieve from the scanned
data. Through a CAD- surface data, altered data are transmitted to model reconstruction system software and changed into a conceptual model Sokovik et al.,
2005. Apart from that, Raja 2007 enlisted the accurate scanning technique which starts
with preparing the part to be scanned and proceed with performing the actual scanning to record details that traces all geometric feature of the part such as steps,
slot, pockets, and holes. The next phase is point processing which involves transmitting the point cloud data,
minimizing noise in the data collected and lessening the number of points. Multiple scan data can be combined to ensure that there are no required features are missed
during scanning. Good datum planning for multiple scanning will cut the effort required in the point processing phase and also hinder introduction of errors from
adjoining multiple scan data Raja, 2007.
2.5 Definition of Rapid Prototyping
Liou 2008 reviewed rapid prototyping as a physical modelling of a design that is generated from a distinct machine technology, implicating adding and bonding
materials in layers to form object. Meanwhile Gibson 2005 defined rapid prototyping as a representation of
technologies that allow the automated fabrication of physical objects instantaneously from virtual 3D CAD data without require any process planning that are relate with
part feature and geometry. Removing material from bar, sheet or rod stock until the right geometry is achieved
is considered as subtractive manufacturing. In contrast with subtractive manufacturing, additive manufacturing utilizes less material and therefore minimum
waste and manufacturing costs Meissner, March 2012.
2.6 Advantages of Rapid Prototyping
12 Rapid prototyping is a quick process since human effort is not required to run the
machine. The process starts by pushing several buttons after completing a virtual model Liou, 2008.
In an article entitled Additive Manufacturing: Pursuing the Promise August 2012, the writer discussed additive manufacturing is not only applicable for various
materials but also does not bear the cost, time, tooling and overhead as are consumed in the traditional machining. Materials such as metals, polymers, composites, or other
powders are applicable to print variant of functional components, layer by layer, including intricate structures that are hardly to be manufactured by other means.
Rapid prototyping offers new design flexibility, minimizing energy use with a promising 50 or greater energy saving, and shorten time to market.The applications
of rapid prototyping are vastly implemented in defense, aerospace, healthcare industry, and automotive industry Additive Manufacturing, August 2012.
Figure 2.2.: The data flow of the basic rapid prototyping RP process Liou, 2008.
2.7 Vacuum Casting
